Modern exhaust systems of combustion engines can be equipped with an SCR-system, in order to reduce the NOX-emissions. Such an SCR-system comprises a reduction agent feeding device, with the help of which a suitable reduction agent, such as for example aqueous urea solution can be introduced into an exhaust gas stream. Furthermore, an SCR-catalytic converter is arranged downstream of the reduction agent feeding device, which reduces nitric oxides to water by means of ammonia. In order to make it possible that this reduction in the SCR-catalytic converter can duly proceed, the reduction agent introduced in liquid form has to be largely evaporated up to the SCR-catalytic converter and intermixed with the exhaust gas stream as homogeneously as possible. In particular, this mixing section, which designates the distance from the reduction agent feeding device to the SCR-catalytic converter, can also be utilized in order to convert the urea introduced in aqueous solution into ammonia and carbon dioxide by means of hydrolysis reaction. To this end, a thermolysis, during which the urea is converted into ammonia and isocyanic acid initially takes place. The actual hydrolysis, during which the isocyanic acid is converted into ammonia and carbon dioxide by means of water, takes place after this.
In order to improve the homogenization, the evaporation and if applicable the hydrolysis it is known to arrange at least one static mixer in said mixing section.
From DE 2 006 017 A2 a static mixer is known, which consists of an annular body, which comprises a blade row with a plurality of guide blades standing away from the annular body towards the inside. With the known mixer, the annular body together with the guide blades is formed by a shaped sheet metal part, which is produced from a single sheet metal body through forming. To this end, a blank in the form of a flat sheet metal body is initially multiply incised in order to cut the guide blades clear. Following this, the guide blades are angled off from the rest of the sheet metal body. After this, the sheet metal body with angled-off guide blades is bent about an axis running transversely to its longitudinal direction until the circumferential ends meet. The production thus takes place in multiple steps, which is comparatively expensive, at least time-consuming.
The present invention deals with the problem of stating an improved or at least a different embodiment for a static mixer of the type mentioned above, which is characterized in particular by an economical producibility. According to the invention, this problem is solved through the subjects of the independent claims. Advantageous embodiments are the subject of the dependent claims.